(1) Field of the Technology
The present technology relates to a toner cartridge for use in image forming apparatuses such as laser beam printers, multifunctional machines and the like and an image forming apparatus using this cartridge, in particular relating to a replaceable toner cartridge for storing toner as well as relating to an image forming apparatus using the cartridge.
(2) Description of the Prior Art
Conventionally, image forming apparatuses using static electrophotography usually include the processing steps of charging, exposure, development, transfer, separation, cleaning, charge erasing, fixing and the like.
In the image forming apparatus thus configured, the process for image forming is achieved as follows. That is, the surface of a photoreceptor that is rotationally driven is uniformly electrified by a charging device (charging step). Then, the photoreceptor surface thus electrified is illuminated with a laser beam from an exposure device to form an electrostatic latent image (exposure step). Subsequently, the electrostatic latent image on the photoreceptor is developed by a developing device to form a toner image on the photoreceptor surface (developing step). The toner image on the photoreceptor is transferred to a transfer medium by a transfer device (transfer step), the toner image is then heated by a fixing device and fixed to the transfer medium (fixing and separation steps). On the other hand, the residual toner remaining on the photoreceptor drum surface after the transfer step is removed by a cleaning device and collected into a predetermined collecting portion (cleaning step). The photoreceptor surface after cleaning is cleared of residual charge by a charge erasing device to prepare for a next image forming operation (charge erasing step).
In the image forming apparatus of this kind, a Mono-component developer consisting of a toner only or a dual-component developer consisting of a toner and a carrier is usually used.
Since a mono-component developer does not use any carrier, there is no need to have an agitating mechanism for mixing toner and carrier uniformly. Hence the developing device has the advantage of a simple structure. However, there is a drawback that the amount of static charge on the toner is unlikely to be stable.
On the other hand, since a dual-component developer needs to have an agitating mechanism for mixing the toner and carrier uniformly, there is a drawback that the developing device is complex. However, since the developer presents stable toner charging performance and suitability to high-speed machines, it is often used for high-speed image forming apparatuses and color image forming apparatuses.
When the dual-component toner is used, the toner in the developer is consumed every time a developing operation is performed. To deal with this, a toner cartridge that supplies toner to the developing device in accordance with consumption of the toner is provided.
The toner cartridge stores toner therein and discharges the toner from a toner discharge port. There are a number of known mechanisms including a system that supplies toner to the developer by discharging toner by means of a screw auger (screw-like toner conveying member), a sponge roller or the like, a system that supplies toner to the developing device as the toner container itself rotates to discharge the toner, and other systems.
Of these mechanisms, the system using an auger screw is ready to control the amount of supplied toner, hence has the advantage that toner can be directly supplied to the developer without use of an intermediate hopper. On the other hand, the toner is prone to be compressed while being conveyed by rotation of the auger screw, and the compressed toner impedes rotation of the auger screw, posing a problem of the auger screw being stuck.
To deal with this problem, as one of the prior art there is a disclosure (see Patent Document 1: Japanese Patent Application Laid-open 2000-214667) in which the conveying spiral (helical blade) of a conveyor auger (screw-formed toner conveying member) is partly cut away so as to reduce the pressure of the toner being conveyed.
However, in the toner cartridge disclosed in Patent Document 1, when the toner conveying member is started to rotate with the toner that is low in fluidity after the toner cartridge has been left for long time, the toner cannot be smoothly discharged from the toner discharge port, but becomes compressed so that the clumping toner builds up around the toner discharge port, causing the problem that the toner conveying member becomes stuck (or referred to as ‘locked’ hereinbelow).